Fiber optic cables are used to transmit light in fiber-optic communications and optical sensing. For example, in optical sensing, properties of light including its amplitude, phase, and frequency or some combination of those properties can represent various signal types, such as temperature, pressure, strain, acceleration, and the like. In some applications, optical sensing can be used in a wellbore by communicating light between a source and downhole sensors or actuators (or both) along a fiber optic communication path. Fiber optic sensing systems implemented in wellbores can include, e.g., fiber optic cables embedded in or attached to the wellbore's casing (or both), or run down into the wellbore with a well tool (e.g., a logging tool string in a drill pipe string). Fiber optic sensors, that sense parameters of interest in a wellbore can be interrogated by an above-ground instrument that includes optical components such as an optical source and an optical receiver. The optical sensor interrogation systems may be positioned such that they are exposed to disturbances including, e.g., acoustic and vibrational disturbances, caused by multiple sources. Due to the design of most optical sensing methods, these disturbances do not significantly affect the sensor parameter information contained in the light signal as it travels along a fiber optic sensing cable. However, as the light travels within the interrogation system on the surface, disturbances to the sensitive optical circuits within the interrogator can result in distortions to the sensor parameter information contained within the light signal.
Like reference numbers and designations in the various drawings indicate like elements.